1 /* Support for an sbrk-like function that uses mmap. */
3 /* Copyright (c) 2010-2014. The SimGrid Team.
4 * All rights reserved. */
6 /* This program is free software; you can redistribute it and/or modify it
7 * under the terms of the license (GNU LGPL) which comes with this package. */
9 /* Copyright 1992, 2000 Free Software Foundation, Inc.
11 Contributed by Fred Fish at Cygnus Support. fnf@cygnus.com */
14 #include <unistd.h> /* Prototypes for lseek */
22 #include "mmprivate.h"
25 #define MAP_ANONYMOUS MAP_ANON
28 #define PAGE_ALIGN(addr) (void*) (((long)(addr) + xbt_pagesize - 1) & \
29 ~((long)xbt_pagesize - 1))
31 /* Return MAP_PRIVATE if MDP represents /dev/zero. Otherwise, return
33 #define MAP_PRIVATE_OR_SHARED(MDP) (( MDP -> flags & MMALLOC_ANONYMOUS) \
37 /* Return MAP_ANONYMOUS if MDP uses anonymous mapping. Otherwise, return 0 */
38 #define MAP_IS_ANONYMOUS(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
42 /* Return -1 if MDP uses anonymous mapping. Otherwise, return MDP->FD */
43 #define MAP_ANON_OR_FD(MDP) (((MDP) -> flags & MMALLOC_ANONYMOUS) \
47 /** @brief Add memoty to this heap
49 * Get core for the memory region specified by MDP, using SIZE as the
50 * amount to either add to or subtract from the existing region. Works
51 * like sbrk(), but using mmap().
53 * It never returns NULL. Instead, it dies verbosely on errors.
56 * @param size Bytes to allocate for this heap (or <0 to free memory from this heap)
58 void *mmorecore(struct mdesc *mdp, ssize_t size)
61 void *result; // please keep it uninitialized to track issues
62 off_t foffset; /* File offset at which new mapping will start */
63 size_t mapbytes; /* Number of bytes to map */
64 void *moveto; /* Address where we wish to move "break value" to */
65 void *mapto; /* Address we actually mapped to */
66 char buf = 0; /* Single byte to write to extend mapped file */
69 /* Just return the current "break" value. */
70 result = mdp->breakval;
72 } else if (size < 0) {
73 /* We are deallocating memory. If the amount requested would cause
74 us to try to deallocate back past the base of the mmap'd region
75 then die verbosely. Otherwise, deallocate the memory and return
76 the old break value. */
77 if (((char *) mdp->breakval) + size >= (char *) mdp->base) {
78 result = (void *) mdp->breakval;
79 mdp->breakval = (char *) mdp->breakval + size;
80 moveto = PAGE_ALIGN(mdp->breakval);
82 (size_t) (((char *) mdp->top) - ((char *) moveto)) - 1);
85 fprintf(stderr,"Internal error: mmap was asked to deallocate more memory than it previously allocated. Bailling out now!\n");
89 /* We are allocating memory. Make sure we have an open file
90 descriptor if not working with anonymous memory. */
91 if (!(mdp->flags & MMALLOC_ANONYMOUS) && mdp->fd < 0) {
92 fprintf(stderr,"Internal error: mmap file descriptor <0 (%d), without MMALLOC_ANONYMOUS being in the flags.\n",mdp->fd);
94 } else if ((char *) mdp->breakval + size > (char *) mdp->top) {
95 /* The request would move us past the end of the currently
96 mapped memory, so map in enough more memory to satisfy
97 the request. This means we also have to grow the mapped-to
98 file by an appropriate amount, since mmap cannot be used
100 moveto = PAGE_ALIGN((char *) mdp->breakval + size);
101 mapbytes = (char *) moveto - (char *) mdp->top;
102 foffset = (char *) mdp->top - (char *) mdp->base;
105 /* FIXME: Test results of lseek() */
106 lseek(mdp->fd, foffset + mapbytes - 1, SEEK_SET);
107 test = write(mdp->fd, &buf, 1);
109 fprintf(stderr,"Internal error: write to mmap'ed fd failed! error: %s", strerror(errno));
114 /* Let's call mmap. Note that it is possible that mdp->top
115 is 0. In this case mmap will choose the address for us.
116 This call might very well overwrite an already existing memory mapping
117 (leading to weird bugs).
119 mapto = mmap(mdp->top, mapbytes, PROT_READ | PROT_WRITE,
120 MAP_PRIVATE_OR_SHARED(mdp) | MAP_IS_ANONYMOUS(mdp) |
121 MAP_FIXED, MAP_ANON_OR_FD(mdp), foffset);
123 if (mapto == MAP_FAILED) {
125 fprintf(stderr,"Internal error: mmap returned MAP_FAILED! error: %s\n",strerror(errno));
126 sprintf(buff,"cat /proc/%d/maps",getpid());
127 int status = system(buff);
128 if (status == -1 || !(WIFEXITED(status) && WEXITSTATUS(status) == 0))
129 fprintf(stderr, "Something went wrong when trying to %s\n", buff);
135 mdp->base = mdp->breakval = mapto;
137 mdp->top = PAGE_ALIGN((char *) mdp->breakval + size);
138 result = (void *) mdp->breakval;
139 mdp->breakval = (char *) mdp->breakval + size;
141 /* Memory is already mapped, we only need to increase the breakval: */
142 result = (void *) mdp->breakval;
143 mdp->breakval = (char *) mdp->breakval + size;
149 void *__mmalloc_remap_core(xbt_mheap_t mdp)
151 /* FIXME: Quick hack, needs error checking and other attention. */
153 return mmap(mdp->base, (char*) mdp->top - (char*) mdp->base,
154 PROT_READ | PROT_WRITE | PROT_EXEC,
155 MAP_PRIVATE_OR_SHARED(mdp) | MAP_FIXED, mdp->fd, 0);